if you do a free space wipe then eraser works by creating thousands of small files as it overwrites the free space. These files will have a creation date, as well as all being 0kb in size once the eraser program has run.
If you are deleting files by using the context menu then there will still be a record that the program was run. You'd have to constantly remove the entire eraser program to avoid this, as well as clearing out the prefetch folder and perhaps remove some entries from the registry (eg MRU programs). Quite a laborious exercise.
far better to not do anything that would lead to someone wanting to do a forensic check on your computer!